Ink stamps which utilize a die for imparting a design or printed message on a suitable surface have found usefulness in a variety of settings. Such stamps typically are utilized in combination with an ink pad containing a supply of ink. When using the stamp, the die is pressed against the ink pad, thereby coating the die with a thin layer of ink. When the die is subsequently pressed against a surface, a design corresponding to that found on the die is imprinted on the surface.
A primary disadvantage to such stampers is the inconvenience of having to use the stamper with an ink pad, which in many cases is not part of the stamper. A supply of the ink for the pad is also required. Additionally, the use of such ink pads frequently results in the uneven application of ink to the die. The amount of ink applied to the die by the ink pad also varies according to the pressure applied on the die; thus, it can be difficult to ensure that the same amount of ink is applied to the die during successive applications of ink to the die.
As a result of these disadvantages, ink stamps having a self-contained supply of ink have been developed wherein the die material is saturated with ink. No pad is needed, nor is pre-inking required, since the die contains the ink. Such a die is described in U.S. Pat. Nos. 3,832,947 and 4,022,127. Ink stamps of this type typically have the die mounted to a die holder. The die holder is, in more sophisticated stampers of this type, attached to a shaft which, in turn, is attached to a cap or handle. Surrounding the die is a shroud or cover skirt. The die holder is normally biased to a position within the cover skirt, such that the cover skirt extends beyond the face of the die.
To use the ink stamp, the stamp is set upon the surface to be imprinted with the cover skirt resting on the surface. A vertical force is applied to the handle which force overcomes the biasing force between the cover skirt and the handle and pushes the die into contact with the surface to be imprinted, where it can then be pressed firmly against that surface.
To provide a consistent impression, the distance the die can be pushed beyond the edge of the cover skirt is limited, as by the distance the handle can travel. For instance, a stop to prevent further travel of the handle can be used to define the stroke or maximum distance of travel of the die, which moves axially with the handle.
With use, however, the die contracts. Additionally, as the ink in the stamp becomes used, it is necessary to apply a greater pressure on the stamp to obtain a quality of imprint consistent with that when the die was newer. Thus, to remain effective, the stamper must be adjustable so that any contraction and ink loss of the die may be compensated for, as by increasing the distance the handle may be pushed down (i.e., increasing the stroke.
An effective means for adjusting the stroke is by permitting the distance between the die and the handle to be adjusted, i.e. allowing for adjustability of the effective length of the shaft which connects the die holder and the handle. This is commonly accomplished by attaching the handle to the shaft with a threaded connection.
Accordingly, to increase the effective length of the shaft, the handle may be "unscrewed" a few turns thereby lengthening the distance between the handle and the die. Thus, when the handle is pushed against its biasing force and towards the cover skirt, it must travel a greater distance before coming into contact with the stop, thereby increasing the stroke.
It is desirable to ensure that the stroke remains set once adjusted. Mechanisms to prevent inadvertent rotation of the handle while using the stamp have therefore been developed. One such using a locking mechanism is disclosed in U.S. Pat. No. 4,203,362.
In the '362 disclosure, a locking member fits between the cover skirt and the handle. One end of the locking member is configured to fit within the handle to prevent relative rotational movement with respect to the handle. On its other end, the locking member has a plurality of ribs which mate with corresponding projections in the end of the cover skirt. When the ribs of the locking member are in mating connection with the projections on the cover skirt, relative rotational movement between the cover skirt and the locking member is prevented. Thus, the locking member provides a positive lock which prevents rotational movement between the handle and the cover skirt.
To adjust the stroke of the '362 stamper, the locking member must be moved upwardly along the shaft of the handle, thereby removing the ribs from mating connection with the projections on the cover skirt. In this position, the handle is free to rotate on its threaded connection with the shaft.
A similar mechanism is disclosed in U.S. Pat. No. 4,649,819. It differs from the '362 locking mechanism in the type of ribs and projections utilized to prevent relative rotational movement between the locking member and the cover skirt. The '819 utilizes tapered teeth in the locking member and corresponding tapered teeth in the cover skirt. The locking action can be overcome either by using the aforementioned procedure whereby the locking member is disengaged, or by rotation of the handle with sufficient force to overcome the engagement.
A primary disadvantage to the mechanisms disclosed in both of the foregoing patents is that their manufacture is complicated by the use of the locking member. The locking member is a separate part to be produced and then assembled. This increases manufacturing costs of the stamp, an item which must be produced at a low cost if it is to be commercially successful. Adjustment also entails two different movements: one being the rotary movement of the handle, the other being the axial movement of the locking member.
The locking member of the '819 stamper also acts as a stop as the handle is depressed towards the cover skirt. Thus, if one attempts to adjust the stamp while the handle is in the depressed position, a sufficient torsional force applied to the handle could deform and/or break the teeth or ribs which prevent relative movement between the locking member and the base.
Yet another adjustment mechanism of this general type is disclosed in U.S. Pat. No. 4,594,943. Similar to both the '362 and the '819 patents, the stamper of the '943 patent utilizes the base as one element of an anti-rotation mechanism. As can be seen by reference to the disclosure of the '943 patent, the components which comprise the mechanism are somewhat complex in their design, and the adjustment mechanism requires some precision in manufacture and assembly.